Vibratory machines are useful in many applications for performing a wide variety of functions including consolidation of disintegrated materials; disintegration of consolidated materials; loosening, separation and transfer of particulate materials; and various machining, finishing and surface treatment operations.
For example, a vibratory finishing machine includes a tub for receiving suitable finishing media along with piece parts to be finished. The finishing media typically comprises a mixture of abrasive material and a suitable liquid, such as water, and may also include a finishing agent. The tub is supported for vibratory motion, and some type of eccentric actuator is employed to gyrate the tub and thereby effect relative movement between the piece parts and finishing media therein to perform the desired function. Polishing, deburring and other finishing operations can thus be performed rapidly on many piece parts simultaneously.
The vibratory machines currently available typically employ eccentric actuators including either a rotatable shaft with eccentric weights mounted thereon, or simply a rotatable eccentric shaft. In either case, the shaft of the eccentric actuator is supported by antifriction bearings of the ball, roller, tapered roller or needle type. However, several problems have arisen in the use of bearings with rolling and non-rolling elements in operating a vibratory machine. The useful lives of such bearings are relatively short because repeated radial loads cause fatigue and localized heat build up leading to early bearing failure. Replacement of the bearings supporting eccentric actuators has been a continual and stubborn problem in the use of vibratory machines.
More recently, hydrodynamic bearings have been employed to support the eccentric actuator in a vibratory machine. Such bearings utilize a thin film of fluid between relative moving parts to reduce the fatigue and heating problems otherwise accompanying direct mechanical contact between the parts. Circulation of the fluid has been especially effective in controlling heat build up in such bearings. Sudden failure can occur, however, if adequate fluid is not maintained between relatively moving parts within a hydrodynamic bearing. Rapid heating due to direct contact between moving parts can occur without adequate hydrodynamic film.
Maintenance of sufficient fluid film within a hydrodynamic bearing has therefore been a critical problem in utilizing such bearings to support the eccentric actuator of a vibrating machine. This has been a particularly difficult problem due to the structural deflection and misalignment which occur during operation of a vibratory actuator, and several attempts have been made to solve it. For example, U.S. Patent No. 3,954,309 assigned to the assignee hereof, discloses a vibrating machine which incorporates the principle of deflection matching between the shaft of the eccentric actuator and the housing within which the hydrodynamic bearings are supported. This approach is effective but somewhat expensive due to the engineering and manufacturing steps that are required to achieve deflection matching. Other approaches have been less effective but equally expensive.
A need has thus arisen for an improved vibratory actuator of inexpensive construction which minimizes structural deflection and misalignment to facilitate maintenance of the proper fluid film in the hydrodynamic bearing.